Calculators may be equipped with graphics capabilities. These calculators are generally special purpose computers with built-in software for drawing graphs. Upon the specification of a function, the graphics calculator is able to plot the function on a predefined set of axes. Such graphics calculators have been pedagogically employed as effective mathematics teaching tools. Educators can easily and quickly plot a variety of mathematical equations to demonstrate the interrelationship between the mathematical expressions and their corresponding graphs. Abstract mathematical concepts are thus more easily grasped by the students.
However, a serious limitation of graphics calculators heretofore has been their limited ability to provide numerical information in support of the plotted graph. Although numerical information about plotted functions can sometimes be obtained, the procedures to do so are awkward and the information is not displayed in a convenient manner. Without this capability, useful and sometimes vital information about the function, such as zeros, local maxima, and local minima, is not readily available. Accordingly, a need has arisen to provide the capability to supply desirable numerical information in support of the graphics function in a graphics calculator or computer.